/*!
 * Bootstrap Grunt task for parsing Less docstrings
 * http://getbootstrap.com
 * Copyright 2014-2015 Twitter, Inc.
 * Licensed under MIT (https://github.com/twbs/bootstrap/blob/master/LICENSE)
 */

'use strict';

var Markdown = require('markdown-it');

function markdown2html(markdownString) {
    var md = new Markdown();

    // the slice removes the <p>...</p> wrapper output by Markdown processor
    return md.render(markdownString.trim()).slice(3, -5);
}


/*
Mini-language:
  //== This is a normal heading, which starts a section. Sections group variables together.
  //## Optional description for the heading

  //=== This is a subheading.

  //** Optional description for the following variable. You **can** use Markdown in descriptions to discuss `<html>` stuff.
  @foo: #fff;

  //-- This is a heading for a section whose variables shouldn't be customizable

  All other lines are ignored completely.
*/


var CUSTOMIZABLE_HEADING = /^[/]{2}={2}(.*)$/;
var UNCUSTOMIZABLE_HEADING = /^[/]{2}-{2}(.*)$/;
var SUBSECTION_HEADING = /^[/]{2}={3}(.*)$/;
var SECTION_DOCSTRING = /^[/]{2}#{2}(.+)$/;
var VAR_ASSIGNMENT = /^(@[a-zA-Z0-9_-]+):[ ]*([^ ;][^;]*);[ ]*$/;
var VAR_DOCSTRING = /^[/]{2}[*]{2}(.+)$/;

function Section(heading, customizable) {
    this.heading = heading.trim();
    this.id = this.heading.replace(/\s+/g, '-').toLowerCase();
    this.customizable = customizable;
    this.docstring = null;
    this.subsections = [];
}

Section.prototype.addSubSection = function (subsection) {
    this.subsections.push(subsection);
};

function SubSection(heading) {
    this.heading = heading.trim();
    this.id = this.heading.replace(/\s+/g, '-').toLowerCase();
    this.variables = [];
}

SubSection.prototype.addVar = function (variable) {
    this.variables.push(variable);
};

function VarDocstring(markdownString) {
    this.html = markdown2html(markdownString);
}

function SectionDocstring(markdownString) {
    this.html = markdown2html(markdownString);
}

function Variable(name, defaultValue) {
    this.name = name;
    this.defaultValue = defaultValue;
    this.docstring = null;
}

function Tokenizer(fileContent) {
    this._lines = fileContent.split('\n');
    this._next = undefined;
}

Tokenizer.prototype.unshift = function (token) {
    if (this._next !== undefined) {
        throw new Error('Attempted to unshift twice!');
    }
    this._next = token;
};

Tokenizer.prototype._shift = function () {
    // returning null signals EOF
    // returning undefined means the line was ignored
    if (this._next !== undefined) {
        var result = this._next;
        this._next = undefined;
        return result;
    }
    if (this._lines.length <= 0) {
        return null;
    }
    var line = this._lines.shift();
    var match = null;
    match = SUBSECTION_HEADING.exec(line);
    if (match !== null) {
        return new SubSection(match[1]);
    }
    match = CUSTOMIZABLE_HEADING.exec(line);
    if (match !== null) {
        return new Section(match[1], true);
    }
    match = UNCUSTOMIZABLE_HEADING.exec(line);
    if (match !== null) {
        return new Section(match[1], false);
    }
    match = SECTION_DOCSTRING.exec(line);
    if (match !== null) {
        return new SectionDocstring(match[1]);
    }
    match = VAR_DOCSTRING.exec(line);
    if (match !== null) {
        return new VarDocstring(match[1]);
    }
    var commentStart = line.lastIndexOf('//');
    var varLine = commentStart === -1 ? line : line.slice(0, commentStart);
    match = VAR_ASSIGNMENT.exec(varLine);
    if (match !== null) {
        return new Variable(match[1], match[2]);
    }
    return undefined;
};

Tokenizer.prototype.shift = function () {
    while (true) {
        var result = this._shift();
        if (result === undefined) {
            continue;
        }
        return result;
    }
};

function Parser(fileContent) {
    this._tokenizer = new Tokenizer(fileContent);
}

Parser.prototype.parseFile = function () {
    var sections = [];
    while (true) {
        var section = this.parseSection();
        if (section === null) {
            if (this._tokenizer.shift() !== null) {
                throw new Error('Unexpected unparsed section of file remains!');
            }
            return sections;
        }
        sections.push(section);
    }
};

Parser.prototype.parseSection = function () {
    var section = this._tokenizer.shift();
    if (section === null) {
        return null;
    }
    if (!(section instanceof Section)) {
        throw new Error('Expected section heading; got: ' + JSON.stringify(section));
    }
    var docstring = this._tokenizer.shift();
    if (docstring instanceof SectionDocstring) {
        section.docstring = docstring;
    } else {
        this._tokenizer.unshift(docstring);
    }
    this.parseSubSections(section);

    return section;
};

Parser.prototype.parseSubSections = function (section) {
    while (true) {
        var subsection = this.parseSubSection();
        if (subsection === null) {
            if (section.subsections.length === 0) {
                // Presume an implicit initial subsection
                subsection = new SubSection('');
                this.parseVars(subsection);
            } else {
                break;
            }
        }
        section.addSubSection(subsection);
    }

    if (section.subsections.length === 1 && !section.subsections[0].heading && section.subsections[0].variables.length === 0) {
        // Ignore lone empty implicit subsection
        section.subsections = [];
    }
};

Parser.prototype.parseSubSection = function () {
    var subsection = this._tokenizer.shift();
    if (subsection instanceof SubSection) {
        this.parseVars(subsection);
        return subsection;
    }
    this._tokenizer.unshift(subsection);
    return null;
};

Parser.prototype.parseVars = function (subsection) {
    while (true) {
        var variable = this.parseVar();
        if (variable === null) {
            return;
        }
        subsection.addVar(variable);
    }
};

Parser.prototype.parseVar = function () {
    var docstring = this._tokenizer.shift();
    if (!(docstring instanceof VarDocstring)) {
        this._tokenizer.unshift(docstring);
        docstring = null;
    }
    var variable = this._tokenizer.shift();
    if (variable instanceof Variable) {
        variable.docstring = docstring;
        return variable;
    }
    this._tokenizer.unshift(variable);
    return null;
};


module.exports = Parser;
